晚上，如果你注意看行车的前大灯，或者在电影院里留意一下放映机，再或者注

At night, if you look at the headlights of traffic, or watch it in the cinema projector, and then note in the dark or open the flashlight, you will find we can not see them hit the beam, unless there is rain in front of them, smoke, dust, or the like dispersed substances.

晚上，如果你注意看行车的前大灯，或者在电影院里留意一下放映机，再或者注意一下在暗处打开的手电筒，会发现我们根本看不到它们打出的光束，除非在它们前方出现雨水、烟雾、或者灰尘等弥散物质。

At night, if you pay attention to the headlights, or the projector in the cinema, or the flashlight turned on in the dark, we will find that we can't see the light they give out at all, unless there is rain, smoke, or dust in front of them.<br>